TAXONOMY 283 



SUBDIVISION I HEPATIC^ OR LIVERWORTS 



Plants of aquatic or terrestial habit whose bodies consist of a 

 rather flat, furchate branching thallus or leafy branch which is 

 dorsoventral (having distinct upper and lower surface) ; the upper 

 surface consists of several layers of cells containing chlorophyll, 

 which gives the green color to the plants; the lower surface gives 

 origin to hair-like outgrowths of the epidermal cells serving as absorp- 

 tive parts and called rhizoids. Upon the dorsal surface of this thal- 

 loid body (the gametophyte) cup-like structures are produced called 

 cupules which contain special reproductive bodies called gemma, 

 these being able to develop into new gametophytes. The sex organs 

 are of two kinds, male and female. The male organs are termed 

 antheridia, the female, archegonia. The antheridia are more or less 

 club-shaped, somewhat stalked organs consisting of an outer layer of 

 sterile cells investing a mass of sperm mother-cells from which are 

 formed the spirally curved biciliate antherozoids, or male sexual cells. 

 The archegonia are flask-shaped organs consisting of an investing 

 layer of sterile cells surrounding an axile row of cells, the neck-canal 

 cells, ventral-canal cells and the egg or female sexual cells. Every 

 ell of the axial row breaks down in the process of maturation with 

 the exception of the egg which remains in the basal portion. Both 

 antheridia and archegonia generally arise on special stalks above the 

 dorsal surface. After the egg is fertilized by a antherozoid, the 

 young embryo resulting grows into a sporogonium (the sporophyte) 

 consisting of a stalk portion partly imbedded in the archegonium 

 surmounting a sporangium or capsule in which spores are produced. 

 When mature the capsule splits open discharging the spores. The 

 spores on germination develop into a protonema or filamentous 

 outgrowth which later develops the thallus. 



Order i. Marchantiales, including Marchantia and Riccia. 

 Order 2. Jungermanniales, the leafy liverworts, including 

 Porella. 



Order 3. Anthocerotales, having the most complex sporo- 

 phyte generations among liverworts, including Anthoceros, and 

 Megaceros. 



